Device for the transmission of vibratory energy



March 27, 192s. I 1.663384 H. C. HARRISON l DEVICE FOR THE TRANSMISSION OF VIBRATORY ENERGY med May 5, `1924 S 50 2a ////,l'////////; 'z 5 l* Mw '6,2

uniformly Patented Mar. 27, 192s.

" UNITED STATES-PATENT OFFICE.

HENRY NEW YORK.

nnvin non 'rn This invention relates to mechanical sys-.

C; HARRISON, OF PORT WASHINGTON, ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A. CORPORATION OF NEW YORK, ASSIGNOR TO WESTERN E TRANSMISSION OF VIBRA-TORY ENERGY.

Application led May 5, 1924. Serial No. 711,044. i

tems for transmittingl vibratory energy and has for its object to improve the transmission characteristics ot such systems.

As pointed out in m filed October 16,

y application Serial 1923, for the iindistorted transmission of multi-frequency energy Waves,lsuch as music, through those of speech or a mechanical transmission line, each portion of the line should have substantially the same characteristic impedance throughout the frequency range to be transmitted as the and following it.

portions immediately For convenience, it is preferable to construct the mechanical line sothat it impedance substantially the frequency range. above referred to, there types-of loaded be incorporated in systems to secure characteristic.

the

has a characteristic constant throughout In the application are disclosed several mechanical lines which may mechanical transmission desired impedance There is disclosed herein a loaded mechanical line which h properties and is particularly adapted for use as a terminating network for a system which would otherwise terminating impedance.

have a. non-uniform As indicated inmy application above referred to, such a line should have'high dissip order that a short length of line may damping in have ation or substantially the characteristics of an infinitely long line. I

have found that an elongated body of vibration dissipating material, such as rubber,

if properly proportioned, has the required characteristics of mass, elasticity, so that it may be given resistance, and dissipation,

a desired character-v istic impedance and so that a veryv short length of it will substantially simulate an infinite line. This me referred loaded electrical line,

as distinguished from a Another feature of chanical line in its form is similar 4to a .continuously having its constants distributed throughout its length,

lump loaded line.

the invention pro- 'vides an improved supporting and balancing means for an armature i n an electromagnetic high dissipative and 14, 15, preferably being secured by short stiff springs, and the balancing is accomplished by providing knee-shaped springs on each side of the pivot, the tension in the springs being adjusted by deforming them at the point olf support.

The invention resides further in the structural arrangements set forth in the following description and claims taken in connection with the accompanying drawings in which Fig. 1 is a front view, Fig. 2 a longitudinal sectional view, and Fig. 3 a transverse sectional view of one embodiment of the invention. Figs. 4 and 5 are detail views of the armature support. Figs. 6 and 7 are a front view and a longitudinal sectional view, respectively. of another form of the invention. Fig. 8 is a longitudinal sectional View of a modification of Fig. 2. Figs. 9 and 10 are a longitudinal sectional View and a transverse sectional view, respectively, of another form of the invention. Fig. 11 shows graphically the characteristics of the device of Figs. 9 and 10.

Referring particularly toFigs. 1, 2, 8 and 9, there is shown an electromagnetic phonograph reproducer or recorder having a permanent magnetlO. An electromagnet may, however, be used if desired. Secured to the magnet 10 are soft iron pole pieces 12, 13

laminated with bevelcd ends, between which is pivotally supported an armature 17, tapered at each end to reduce its mass.. The armature 17 is mounted on an elongated bar 20, preferably e made to vary with the armaof a suitable aluminum alloy, and is'pro- 20/is held on its pivots andthe armature balanced, preferably by the4 resilient supporting and balancing means shown-in detail 1n Figs. 4 and5, and' described hereinafter.

A pair of windings 24and 25 are mountedcoaxially with the amature between the pole pieces and are connected by to a suitable electric circuit. I

The bar 20 is turned downwardly at .its outer end to form a stylus holder 29, ih

leads 426 and 27 which is mounted a phonographic needle 30 in engagement with a record 32. The device may be used either as a recorder of speech and music or as a reproducer thereof. The

larger than the diameter of the bore, and by means of a cord 42 or the like may be positioned atlany desired point within the rubber cylinder for tensioning the spring and thereby holding the rubber cylinder against a plate 34. rl`he end A28 of the bar20 is preferably rectangular in cross-section and slightly tapered, and the plate 34 is provided with a rectangular hole in which the end 28 is held by the tension of the sprin 38 and the rubber tube 36. The rubber cy inder or tube 36 is enclosed in a casing formed of channel-shaped members 45 and 43, and' is preferably. out of contact with the casing so as to avo1d so far as possible friction at the surface of the rubber, which would interfere with the transmission of the vibrationsl By making theein'side dimensions of the channel-shaped members 45 and therethrough.

43 substantially larger than the' diameter of the rubber cylinder or tube, usually no su ports are required' for the tube, but the tngo may, however, vbe supportedits whole length by soft felt or cotton wrapping, as shown'in 7 or at its outer end by-a felt, a cotton or a spongerubber ring as shown in Fig. 8, For most cases, however, it is believed pref- `erable to reinforce the vtube 36 by a thin "metal strip 35, as shown in Figs. 9 andlIO..

This will prevent the rubber line from Sagging and making contact with thecase intermediate its ends.

The rubber line herein described is analo-l gous to a uniformly loaded electrical line.-

The general expression'foil thel impedance Iof any mechanical network is where r is mechanical resistance per unit The rubber line 36 'is in by a wrappmg 48 of soft fabric such as cot-.`

length and corresponds to the electrical re- .66

sistance, g is the mechanical conductance in a unit section of the line and corresponds to the dielectric conductance, or leakage, m the electrical case, M is the mass corresponding to electrical inductance, S is the elastlcity per unit length corresponding to the reciprocal of the capacity in an electrical clrcult.

ture at all fre uencies attentuate equally, these constants s ould have such values that gfgM.

In other words, the conditions requisite for a mechanical line to have` a pure resistance characteristlc impedance are analogouslto those requlsite to an electrical network for pure resistance. The velocity of the arma- In order that the velocities of the armature corresponds to the current in an electrical circuit. By choosin a material .such as will have the proper st1 ness or elastlcity, mass and resistance, the impedance may .therefore be made independent of the frequency, in'which case the velocity of the armature is a faithful copy of the mechanical force in the case of a reproducer or the electromagnetic force in therese of a recorder.

The rubber line should be olfconsiderable length. At least it shouldbe long enough to dissipate practically all 'the-energy imparted to it' before it is transmitted from one .end

of the Aline to the other and reflected back to the starting point. -This is desirable since if a considerable portion ofthe transmitted energy is reflected back to the startingpoint, the reflected energy would be in phase for certain frequencies of the impressed vibrations and out of phase for other frequencies,

Ain which case the line would have a variable impedance and hence would not respond with equalmvelocities to equal forces at all frequencies.` If the -material used for` the line has a-small rate of dissipation of motional energy, the line `must be long, while if the material has a high rate of disslpationt,

the line. may be4 short. Excellent results -havebeen obtainedi by means ofa cylindrical line of pure gum rubber nine inches long, one-halfsinch outside diameter and oneuarter inch inside diameter. It is obvious owever that other vibrationv dissipating materials than rubber might be used such as leather, felt, cork, spongy lead. Figs. 6 and 7 show the application of the lnvention to an electromagnetic transmitter.-

The arm 56 in this case is connected by means of a rod 46 to the usual diaphragm 47. this case supported ton or felt, but itmay be supported by. any

of the arrangementsherein described. Although this arran ement may be used as a loud speaking recelvei` it is preferablewhen Y length of the cylinder.

so used to locate the arm 56 between the armature and the rubber line as in the case o the recorder shown in Fig. 9.

In Fig. 8, the rubber line is shown as gradually tapered from the arm 20. This taper may be reversed, depending upon the characteristics desired. The reproducer may be supported on a comparatively heavy meta-l block 50 by a. yoke or U-shaped member 51 pivoted to the case 45 to permit vertical movement and to the block 50 to permit horizontal movement. This arrangement provides a convenient support for the re.- corder andthe reproducer, rendering them portable and readily attachable to any standard type of talking machine.

'In the modification shown in Figs. 9 and 10, the disc 81 is held snugly against the cylinder 36 by means of a strip 35 of aluminum or other suitable material extending the One end of the strip 35 is secured by a rivet or other suitable means to the bar 20 and the tube is secured in place by a pin 52. By slightly compressing the tube longitudinally, the proper' tension is provided to hold the parts together. By arranging the strip iny a vertical plane, sufficient rigidity will be added to the line so that it will not sag and touch the casing. When additional loading is required, the tube 36 may be filled with comminuted material 53 of any desired mass. Small size lead shot has been found to give very satisfactory results. The end of the tube may then be sealed by any suitable Fig. 9 also shows the preferred arrangement for a recorder'. The stylus bar 54C in this case is located between the armature 17 and the rubber line 36 and carries a cutting style 55. A micrometer screw 57attached to the recorder' rests on the record 58 for gauging the depth of the cut in the record. Y l

The preferred ing and balancing Figs. 4 and 5. The supporting member 60 carries the knife edges 61 which engage the recesses 21 and the bar 2() to which the armature 17 is attached by any suitable, means. The bar 20 is held on its knife-edge pivots by a thin rod 62 extending through the mounting 60 and the bar 20. One end of the rod 62 is secured to the mounting 60 by means ofy a plate 63, Whichhas two opposing lugs 64 and 65 sheared from the plate. These lugs are bent outwardly and act as springs and engage the head 66 of the rod 62. The opposite end of the rod 62 projects through the bar 20 and is threaded for a nut 67 to adjust the tensioning rod 62 and the springs 64 and 65. For balancing the armature in the steady. magnetic field, resilient members 68 and 69 are attached to the bar 20 on each side of a pivot. Members 68 arrangement for supportthe armature is shown 1n.

' transmitters,

and 69 are flat knee-shaped springs being f given a slight'bend or initial set, 'as shown at 70 and 71. Their opposite ends are secured to the mounting 60 by means of the U-shaped member 68 and rod 62. The bends 70 and 71 should be of a sufficient angle to permit maximum displacement ofthe armature before members 68 and 69 become straight. The mounting 60 is provided with transverse slots or grooves 72 and 73, into which the springs may be deformed under the pressure of ynuts 74 and 75 to regulate the tension therein and effect a balance of the armar.

ture in the magnetic field.

Fig. -11 shows curves comparing the characteristics of recordersl with and without the rubber line of the invention. The curves are plotted .with velocity in transmission units as ordinates and frequency at constant driving current as abscissae. A transmission unit is defined by the relation.

N 20 logwil, where V1v is the input velocity and V2 is the output velocity, and N the number ofv transmission units by which the-velocities V1 and V2 differ. Curve A is a typical curve showing the characteristic of an improved type ofl damped recorder. It will be noted that although damping was applied in this case,

there is a decided resonance peak at a fre-I capable of faithfully recording both the high and low frequency notes and also the harmonics characteristic of the different instruments. For natural reproduction of recording, it is quite important that the harmonies be faithfully recorded and reproduced in order that the individual instruments may be identified. In the of reproducers, these harmonics are insufficiently registered to make it possible to clearly identify the recording instruments.

While the invention has been illustrated as applied to electromagnetic recording and rcproducing devices it is obvious that it may be applied with advantage to microphone the usual mechanical reproducers and recorders, oscillographs or any mechanical vibrating system.

VV-hat is claimed is: 1. A solid medium for receiving and dissiusual type y pating vibrator-y energy comprising an elon- `gated body of non-metallic vibration absorb- 1n material of a "homogeneous character;E

sald body having precomputed values o mass, elasticit reslstance and d1ss1pat1on per unit'len t i such that the characteristic impedance o saidfbody is substantially const ant throughout a range of frequencies to v be transmitted.

2. A solid medium for receiving and d1ss1- pating vibratory energy according Yto claim A 1 in which said mass, elasticity, resistance, and dissi ation are uniformly distributed t throughout the length of said body. 4

3. In a line for the transmission of vibratory energy, a terminatingportion cpmprising an elongated body of vibratlon d1ss1- patingfmaterial, and means for torsionally vibrating said homogeneous body. '4. In a line for the transmission ofl vibratory energy, a terminating portion therefor comprising an elongated homogeneous l body of vibration-dissipating material having a characteristic impedance substantially equal to thaty of said line throughout a range ture, means for pivotally supporting said armature, an elongated homogeneous body of vibration dissipating material, the axis of said body being in alignment with the axis of oscillation of said yarmature and means securing said/ body to said armature for rotation therewith.

8. In an electromagnetic system, an armature, an elongated member receiving torsional forces from the vibrationI of said armature, a mechanical line of a homogeneous material having a high degree of dissipation connected to the end of sald member remote from said armature, and a recording stylus connected to an intermediate point on said p member. f

9. The combination, of claim 8, in which said mechanical line comprises an elongated body` of rubber.

10. In a system for the transmission,y of mechanical-vlbratory energy, an elastic member, means for producing torsional vibrations in said member, an elongatedl body. of4 4 rubber, and means for securln said body to said member in longitudina alignment therewith. V

11. The combination of claim 10, -in which said body of .rubber is in the form of a tube.

12. The combination of claim 10,'in which' said body is in the' form of a tube, and said securing means lies within said tube.

ing an armature, a ar supporting sai .of said rod to exert tension net, ian armature in t separate tensioning means to balance said armature in the field of said magnet.

15. The combination of claim 14 wherein two lat knee-shaped springs are provided for balancing the armature in the magnetic field, 'and means for deforming the ends of said springs to vary the tension.

16. The combination of a magnet, an armature in the field of said magnet, an oscillatory bar supporting said armature, a

mounting for said bar, a soft rubber cylinv der attached to the end of said bar and coaxial therewith, and a pair of s rings attached to said rod, said rubber cy inder and springs adapted to control the vlbrations of said armature.

17. In an electromagnetic device, a pivoted armature, a mounting for said armature, means for supporting said armature-on its pivots, said means comprising a thinflexible rod extending through the axis of su'pport of "said mounting, and a short spring transverse and engaging said rod to yieldingly maintain said rod under tension.

18. The combination according to claim 17, in which two `short springs engage said rod to yieldingly maintain it under tension.

19. An electromagnetic device according to claim 17, in which the rod is secured between the ends of said springs.

20. An electromagnetic system comprising an armature, a bar supporting said armature, a mounting pivotally lsupporting said ss f bar, tensioning means securing said bar on 1 its pivots, a palr of springs extending from said armature support to said mounting, and means for distorting said sprin transversely tov vary the tension in sai effecting -a balance of said armature.

21. In an electro agnetic system com risarmature, a mounting provi ed with a knife edge a lrod having one end associated with said bar, and a short spring extending transverse said bar and. engagin the other end erein and hold said b ar upon its mountin y, 22. In an electroma netlc device, a mage field of said magnet, a barsuppiorting said armature, a mounting for sai bar and armature, a pair of tensioning members connecting said bar and said armature, said tensioning membersy springs for members to eiect a, change in tension whereby the armature may be balanced in the magnetic eld.

23. The combination of the electromag- 5 netic device of claim 22 and. a. rubber line connected to the end-of said bar for controlling the vibrations' thereof.

24. In a. line for the transmission of vibratory energy, an oscillatory member,` an

elongated body of non-metallic vibration 10 absorbing material forming a longitudinal extension of` the axis of said oscillatory member and adapted'to be torsionally v1- brated thereby.

In witness whereof I hereunto subscribe 15 my name this 2 day of May A. D., 1924.

HENRY C. HARRISON. 

